Luke 23:29

By these days He signifies the time of the siege and captivity which was coming upon them from the Romans, of which He had said before, Woe to them that are with child, and give suck in those days. It is natural, when captivity by an enemy is threatening, to seek for refuge in fastnesses or hidden places, where men may lie concealed. And so it follows, Then shall they begin to say to the mountains, Fall on us; and to the hills, Cover us. For Josephus relates, that when the Romans pressed hard upon them, the Jews sought hastily the caverns of the mountains, and the lurking places in the hills. It may be also that the words, Blessed are the barren, are to be understood of those of both sexes, who have made themselves eunuchs for the kingdom of heaven's sake, and that it is said to the mountains and hills, Fall upon us, and Cover us, because all who are mindful of their own weakness, when the crisis of their temptations breaks upon them, have sought to be protected by the example, precepts, and prayers, of certain high and saintly men.

For behold, the days are coming in which they will say: Blessed are the barren, and the wombs that never bore, and the breasts that never nursed. Then they will begin to say to the mountains: Fall on us; and to the hills: Cover us. He signifies the days of the coming siege and captivity by the Romans. About which he previously said among other things to his disciples: Then those who are in Judea, let them flee to the mountains. And shortly after: Woe to those who are pregnant and nursing in those days (Matthew XXIV). For it is natural, with captivity imminent and hostile destruction raging in the fields and cities, for all who can escape to seek out high places or hidden refuges, where they can hide. And Josephus specifically mentions that, with the Romans pressing upon them, the Jews competitively sought out caves in mountains and hills. So much so that he himself testifies to being discovered, captured, and handed over to the enemies in a hideout in a cave with forty companions during the fall of the fortified city of Jotapata. And it can also be understood superfluously, that those sterile and not giving birth are said to be blessed, referring to those who castrate themselves in either sex for the kingdom of heaven. Saying to the mountains and hills: Fall on us and cover us, when anyone, mindful of their own frailty, during the onset of temptations, seeks to be defended by the example, advice, and prayers of men of lofty status, by virginity, martyrdom, or any other virtue.